A linear motor is provided with a stator and a rotor, which are produced to be similar in principle to those of a rotary motor, but elongated linearly. In the linear motor, electric energy is converted into thrust for moving linearly. For this linear thrust, the linear motor is used as a one-axis actuator to enable a moving object to move linearly.
From a point of view of shapes, the linear motor can be classified into a rod type and a flat type. The rod-type linear motor is provided with a plurality of cylindrical coils which are stacked on one another and a rod having magnets is inserted into a bore (hollow space) formed by the stacked coils. For example, the plural coils are formed as three phases consisting of U, V and W phases. When three-phase currents whose phases are different from each other by 120 degrees are supplied to the coils, magnetic fields are generated to move along the axis-line direction of the coils. These moving magnetic fields give thrust to the rod, resulting in that the rod moves linearly relative to the coils in synchronization with the speed of the moving magnetic fields. In contrast, the flat-type linear motor is provided with a plurality of plate-shaped magnets arranged on a track rail and a plurality of coils arranged to face the track rail. With regard to the linear movement of the coils relative to the magnets, this flat-type linear motor obeys the same principle as the rod-type linear motor.
Coil assembling of the rod-type linear motor is performed as follows. First, coils and spacers to be interposed between coils are fit alternately one after another onto a coil arrangement shaft as a jig. Each of the spacers is ring-shaped and has a function of insulating adjacent coils from each other. Once all of the coils and the spacers are fit thereon, the coils are wired with their phases divided into U, V and W by soldering every three coil lead wires. Each of the soldered lead wires is wrapped with an insulating tube.
However, in the conventional coil assembling method of linear motor, alternate fitting of coils and spacers onto the coil arrangement shaft is followed by coil connecting operations which number of times is equal to the number of coils, and this takes much more time and manpower as the number of coils is larger. Besides, when the coils and spacers are arranged sequentially, there occur variations not only in the coil pitch, but also in the overall length of the coil unit as dimensional differences of the respective coils accumulate.
The patent document 1 discloses a method for assembling a coil unit by inserting coils into a coil guide on a one-by-one basis, or on a two-by-two basis, and laminating a plurality of such coil guides with the coils inserted therein.    Patent document 1: Japanese patent laid-open publication No. 2004-357464